The invention relates to rotary drum type mills, such as ball, rod, pebble or autogeneous mills and particularly to lining structures used in such mills.
Common devices used to grind or comminute solid material, such as ores, are drum-like structures adapted to rotate about a horizontal axis where the charge in the mill is lifted or carried up the ascending side of the drum and tumbles back down over itself producing pulverization of the charge. This pulverizing action can be "autogeneous" through interaction between particles of the charge or may be enhanced by providing grinding media in the mill, such as balls, rods or pebbles, Because of this action, mills of this type are often provided with replaceable interior lining members to protect the mill interior from the impact, abrasion and wear effected by the grinding action. These liners are often fabricated of vulcanized rubber.
Many of the above described mills also include lifter bars secured to various interior surface portions of the mill. These lifter bars are typically provided longitudinally of the mill and at one or both of the annular end closures of the mill. The longitudinal lifter bars are normally disposed at selected circumferential spacings while the lifter bars at the ends of the mill are disposed along spaced radii extending from the axis of rotation.
Liner members or plates are normally positioned between adjacent lifter members and their shape generally reflects the shape of the spaces between adjacent lifters (e.g. liners are generally of rectangular shape when between longitudinal lifters and wedge or pie-shaped when between radial lifters).
When lifter members of metal, such as steel, are used in these rotary members certain problems arise due to the high fastening torque applied to properly secure the lifters to the mill walls. Generally the lateral margins of the lifter bars must forcibly bear upon a lateral margin of an adjacent liner member. It has been found that when using all rubber liners between steel lifters, that this high torque applied causes the margins of the rubber liner to squeeze or pop out from the underside of the lifter bar bearing upon it. Thus, use of all rubber lining members for disposition between such metal lifters have not been entirely satisfactory. It has been proposed to reinforce these rubber liners with steel plates or bars embedded within the margins of the liner member. This, however, adds considerable weight to the liner and thus to the mill as a whole. Also, mill liners with steel reinforced margins are complicated and expensive from a manufacturing standpoint.